Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Costs (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 110	$ 168	$ 225
Expected return on plan assets	(317)	(388)	(357)
Amortization of net actuarial loss	5	2	1
Settlement losses	16	0	0
Net periodic benefit cost (income)	$ (186)	$ (218)	$ (131)